A 28 day, repeat-dose, oral toxicity study of indole-3-carbinol and diindole methane followed by a 28-day recovery period will then be conducted in rats. Endpoints will include food and water consumption, body weight, clinical observation, ophthalmic assessment, clinical chemistry and hematology, plasma test agent levels, urinalysis, and anatomic and histologic pathology. Biochemical evaluation of cytochrome P450 isoenzyme and phase 2 enzyme modulation will be conducted after the 28 day treatment and after the 28 day recovery. Dose associated toxicities will be identified.